Soil aggregation and structural stability in arid Iraqi landscapes: Mechanisms, indicators, and management implications: Subject review

Abstract:

Soil salinization is a very serious problem for agriculture and for maintaining the quality of the land in arid and semi-arid parts of the world, such as Iraq. Our research focuses on the relationships between salinity, aridity, and the structural integrity of soil. Specifically, we looked at various indicators that gauge the stability of aggregates including the Mean Weight Average Diameter (MWD) and the Geometric Mean Diameter (GMD) of soil aggregates. Dispersion of soil aggregates due to saline soil, along with climatic impacts like high rates of evaporation and low rates of precipitation, has reduced the stability of soil aggregates, which in turn has adversely affected the rate of infiltration of water into soils and the growth of roots in the soil. Applying organic matter to soils using manure and legumes increases the formation of aggregates and creates biological binding agents that increase the cohesion of soil. Conversely, using only chemical fertilizers on soils generally leads to decreased aggregate stability because they lead to increased dispersion of clay particles and decreased proliferation of microbial activity in the soil. The influence of soil texture on these situations is evident: clayey soils generally have a much greater innate strength of bonding than sandy soils, but clayey soils require a constant supply of organic matter to maintain their strength of bonding. Overall, the use of saline irrigation water and lack of sufficient drainage cause continued accumulation of salt in the soil, which continues to deteriorate the structural integrity of the soil. Using remote sensing technologies and methods alongside field data provides useful tools for assessing salinity and structural variations on land. The Iraqi agricultural system should use organic amendments and encourage the use of conservation tillage techniques and the reestablishing of vegetation as methods to lessen the impact of salinity while maintaining soil aggregate stability, which will foster productive use over time within the severe environmental conditions typical to the region.